SPF record comparison

Hi all! I am currently trying to set up an SPF record for our domain, and I have gotten stuck. Names have been changed to protect the innocent!

We send and receive email from 3 locations, smtp.domain.com, smtp1.domain.com and smtp2.domain.com. These locations also deal with domain.co.uk email. I need an SPF record to show this. We currently send mail out via dns so I am unsure if I need to use the soft bounce or hard bounce options (~all or -all).

Hi Popowich, sorry for the horrendously late reply, I got stuck on another project. I would rather use the names than the IP's, as the IP's may rarely change and the names will not. In which case, would either of these SPF records work? I am unsure of the correct use of the a: or mx: which is the main difference between the two. Also, I'm new to the record itself so other options such as the soft and hard bounce values are a bit of a Grey area to me too.